2 identify and describe the main regions of alimentary canal describe the functions of the parts of the human gut and the associated organs
3 Pathway of Digestion in Alimentary Canal Mouth↓OesophagusStomachSmall IntestinesLarge IntestinesRectumAnus
4 Digestion is the process of breaking down complex, large molecules (food) into simple, soluble and diffusible molecules so that it can be absorbed by the body and be used to build and nourish cells and to provide energy.
5 Functions of digestive system: (1) Ingestion: taking food into the body.(2) Digestion: breakdown of food materials into smaller amounts (i) Mechanical digestion (ii) Chemical digestion(3) Absorption(4) Assimilation(5) Egestion
6 Types of digestion: (i) Mechanical digestion Break down particles into smaller pieces so as to increase the surface area for the action of enzymes.(ii) Chemical digestionInvolves enzymatic reactions which digest the food into simpler chemical forms.Hydrolysis splits the large molecules by addition of water.
7 How is Food Digested? Mouth Ingestion is the process of taking food into the body.The tongue rolls and lubricates food with mucus and saliva.Chemical digestion of starch starts here by salivary amylase.OesophagusIt takes food down from the throat and into the stomach. Moving food by waves of muscle contraction called peristalsis.
8 The oesophagusThe partially digested food is pushed to the stomach by wave-like contractions known as peristalsis.Circular muscles contract to push the food ball down.Circular muscles relax, and the tube widens for food to move.
9 The stomachStomachThe stomach lining produces mucus and gastric juices which contains:i) hydrochloric acid (acidic medium of pH 2 for enzymes and kills micro-organisms in food)ii) Pepsin: hydrolyze protein to polypeptides.iii) Rennin: hydrolyze milk caseinogen to casein.stomach
10 Quick Revision: What is the function of hydrochloric acid? 1) Provides an acidic medium for activation of gastric enzymes.Inactive formsProrennin HCl RenninPepsinogen HCl Pepsin2) Kills germs and potential parasites.3) Stop the action of salivary amylase.Active forms
11 Case Study 1 You should: take multiple small meal at regular intervals,take less protein permealclean and cook the food thoroughly……Dr. Jones, I am suffering from stomach cancer & half of my stomach was removed.What should I do?
12 Case Study 2Oh dear….i feel that my chest is burning after having a heavy dinner.What could have gone wrong?
13 InflamedoesophagusThis condition is due to the irritation of the oesophagus that is caused bytoo much stomach acid.
14 The Liver & Gall Bladder A small pear-shaped organ that is greenish-yellow in colour.Temporarily stores bile secreted by liver.QUESTION:Will bile secretion be hindered if the gall bladder is removed?
15 Liver and Gall Bladder Pancreas Small intestines Large Intestines THE STRUCTURE & FUNCTIONS OF …Liver and Gall BladderPancreasSmall intestinesLarge IntestinesRectum and Anus
16 Largest gland in the body. LIVER:Largest gland in the body.Lies below diaphragm, on right side of body.Secretes bile.QUESTION: Can bile digest food?Bile is not an enzyme, so it cannot digest food but it aids in digestion of lipids.